1. Field of the Invention
The invention relates to a wire bonding process and a wire-bonding structure. More particularly, the invention relates to a wire-bonding process performed according to reverse bonding fashion.
2. Description of the Related Art
As the era of information technology progresses, the transmission and processing of information and documents are extensively carried out through electronic equipment. Accompanying the progress of technology, many electronic products with more convenient features are promoted with great success, as mobile phones, computers, audio-video articles, etc. Electronic products usually comprise semiconductor devices packaged into electronic packages. An important step in semiconductor device packaging process is the wire bonding that establishes the electrical connection within the electronic package between the semiconductor device and the carrier of the semiconductor device.
Referring to FIG. 1 and FIG. 2, cross-sectional views schematically illustrate the conventional reverse bonding process disclosed in U.S. Pat. No. 5,328,079 issued to Mathew et al. In FIG. 1, the conventional wire-bonding process comprises first, providing a chip 100. The chip 100 has an active surface 102 and a corresponding back surface 104, wherein the active surface 102 further includes at least a first contact pad 106. A substrate 150 is further provided with a surface 152 on which at least a second contact pad 154 is formed, wherein the back surface 104 of the chip 100 is bonded to, for example, the surface 152 of the substrate 150. By means of a wire-bonding machine (not shown), a conductive bump 108 is formed on the first contact pad 106 of the chip 100.
Referring to FIG. 2, a reverse bonding then is performed using the wire-bonding machine. First, a prominence 182 is formed on the second contact pad 154 in ball-bonding fashion. A head of the wire bonding machine (not shown) then moves from the formed prominence 182 to the conductive bump 108 on the first contact pad 106 of the chip 100, wherein the head of the wire-bonding machine continuously releases a conductive material forming a wire 180 while moving. The wire 180 hence formed is bonded to the conductive bump 108 in a stitch-bonding fashion.
In the foregoing wire bonding process, because the conventionally fixed height of the bump 108 is not sufficient, a shorting contact of the wire 180 with the edge of the chip 100 may occur at the location 190 proximate to the edge of the chip 100. As a result, the reliability of the electronic packaging structure is reduced. Moreover, the wire 180 may easily peel off from the bump 108 when the packaging structure is submitted to a contingent external force.